1. Field of Invention
This invention is a monitoring device to detect warning signs indicative in Sudden Infant Death Syndrome (SIDS) and other respiratory or cardiac conditions threatening to infants. It is designed to minimize false alarms, to be easily used by parents or other caregivers who have no special training, to be portable, affordable, and practical.
2. Description of Related Art
Sudden Infant Death Syndrome is the term used to designate the death of seemingly healthy infants commonly between the ages of two weeks and one year. Sudden Infant Death Syndrome [usually abbreviated SIDS, sometimes called crib death] is the leading cause of infant deaths up to the age of one year.
The exact cause of SIDS has not been determined. It has been suggested that SIDS occurs in healthy infants as the result of the occurrence of a series of unrelated events. Infants who have periods of apnea, changes in skin color, changes in muscle tone, or who sometimes require help in breathing are more likely to die of SIDS. It is sometimes thought that the infant's position in the crib is a factor in SIDS, and various arrangements of pillows around the infant have been proposed to reduce the risk of SIDS.
A number of systems have been proposed to alert a parent or other caregiver of physiological changes that may be characteristic of the beginning of a SIDS episode in infants. It is believed if parents have warning of respiratory distress, they can intervene before an episode becomes irreversible. For example, alarm systems have been designed to detect if an infant has stopped breathing or if the infant's heart rate has slowed significantly. These apnea/bradycardia alarm systems have been available for home use since the late 1970's. These alarm systems use electrodes attached to the infant's skin. They provide an audible alarm if the infant stops breathing for a predetermined period or if the heart rate drops below a designated level. However, these instruments require electrodes attached to the infant's skin that are connected to the monitor by wires. The wires can be hazardous to an infant. Further, these types of monitoring systems are subject to false alarms. Many false alarms can lead to reduced watchfulness by the caregivers. Moreover, each false alarm can be a cause of parental anxiety. For a monitoring system to be practical and successful, false alarms must be minimized.
A different technology has been employed to monitor for the beginning of a SIDS episode. This technology uses a pulse oximeter, which monitors the pulse rate and the oxygen saturation in the blood. It is thought that a drop in the oxygen saturation to an unsafe level (hypoxemia) is the first event to occur in the SIDS. As such, the pulse oximeter is a means of monitoring hypoxemia, hence it can give early warning of a SIDS episode. Pulse oximeters operate by measuring a light signal passed through an extremity. This light signal changes, depending on the oxygen saturation of the red blood cells. These probes are typically placed on a finger, toe, hand, or foot of the infant being monitored. Placement on the extremities, however, makes the probe susceptible to motion artifacts. By positioning the O.sub.2 saturation probe on the infant's sternum or back, the motion of the probe, therefore, false alarms may be reduced. However, again, the wires connecting these probes to the central monitoring unit have drawbacks.
One system has been proposed that uses a combination of pulse oximeter, motion detector, and video camera (see Kim, U.S. Pat. No. 5,505,199). This proposes a motion sensor, video camera and pulse oximeter all be placed in the infant's room and connected to a central unit in the monitoring room, usually the parent's room. The Kim '199 patent states claims that the use of a motion detector with a pulse oximeter and with a video monitor is successful in reducing the number of false alarms. However, it requires a video camera and a motion detector and a pulse oximeter all connected to a video monitor. This requires extensive wiring and instrumentation and is prohibitively expensive for most parents. Additionally, it presumes the monitoring will only occur from the location of the central monitoring unit, including the video display. This means that the caregiver must be close to the central monitoring unit while the device is in use. Also the infant must be sleeping in the room equipped with the camera, motion detector, and oximeter.
Pulse oximeters typically use a sensor attached to a finger or other extremity. This sensor is conductively coupled to an electronic device that measures and provides a readout of the percentage of oxygen in arterial blood. For example, the Isaacson et al., U.S. Pat. No. 5,490,523 discloses a pulse oximeter with a miniature measuring readout device attached and incorporating the sensor. The Isaacson design eliminates the conductive cables that connect the sensor to the readout. Isaacson claims the conductive cables can become damaged during use. His design eliminates the connecting cable, hence, eliminates the problem of cable connection failure. The Isaacson et al. patent shows an extremely small, lightweight and durable pulse oximeter that is battery operated.
Many parents or other caregivers utilize a battery-powered, sound-receiving and broadcast unit, often called a baby monitor. The broadcast unit incorporates a microphone with a compact radio transmitter powered by a battery. This is placed by the crib or other sleeping site of an infant. Should the infant wake and begin to cry or make other unusual noises, the sound created by the infant will be received by the microphone and converted to a low-power radio signal, which is broadcast to a portable receiving unit. This receiving unit is also compact, battery-powered, and contains a receiver and speaker to convert the radio signal back into a sound wave. The receiving unit is carries from room to room so if the baby begins to cry, even if in a remote part of the house, the caregiver will hear the cry through the receiving unit, which is kept with him as he moves from room to room in the house. This device will readily allow a parent to intervene in the event the infant is crying. However, SIDS, by its very nature, is a silent event and difficult to detect by monitoring the infant's sounds alone.
It is believed that none of the above described devices provides an effective way for parents to monitor an infant for the beginning of a SIDS event in time to allow the parent or other caregiver to intervene before the event becomes irreversible. For a device to be effective, it should be affordable for parents or other caregivers of even modest means. Second, it should be easily operated and should not require special training. Third, it should be easily attached to the infant and comfortably worn as to not interfere with the normal sleep of the infant. Fourth, it should not require connecting cables or cords in which the infant could get tangled. These cables or cords are subject to failure over time and can pose a danger to an active infant. Fifth, the device should be resistant to false alarms from motion artifacts or other causes. Sixth, it should be portable so that a parent or other caregiver is not tied to a particular room to monitor the SIDS alarm, nor is the infant required to sleep in a particular room. Therefore, both the unit placed on the infant and the unit giving the alarm should both be portable and lightweight.